Infectious diseases you’ve probably never heard of Part IV: CIGUATERA
We’ve all heard of malaria, dengue fever, typhoid fever and hepatitis. These are all common infectious diseases we hear about while traveling, especially in developing countries. But what about the lesser known infectious diseases? Like ciguatera, which is the most frequently reported cause of fish-borne poisoning worldwide. Are you at risk?
What is ciguatera?
Ciguatera is a food-borne illness caused by a neurotoxin called ciguatoxin that accumulates in reef fish. It is produced by small sea algae known as dinoflagellates, which adhere to dead coral, seaweed, and other surfaces in warm, shallow oceans. The toxins are ingested by herbivorous fish, which are then ingested by carnivorous fish causing an accumulation of toxins as they move up the food chain. The toxins are harmless to fish but can act as a poison in humans.
Ciguatera can be found in large reef fish, such as barracuda, grouper, parrot fish, red snapper, amberjack, and moray eel. The disease has been linked to more than 400 species of fish. Ciguatoxin is tasteless, odourless, and fish contaminated with the toxin cannot be identified by appearance. Cooking, freezing, salting, drying, smoking, or marinating the fish will not kill the toxins.
Are you at risk?
There are approximately 50,000 cases of ciguatera poisoning reported annually worldwide. It’s common in tropical and subtropical regions throughout the Caribbean, Indian Ocean, South Pacific islands and Australia. The highest risk is in the east Caribbean Sea. Ciguatera is also a risk in Hawaii, southern Florida, the northern Gulf of Mexico and up the east coast to North Carolina.
The risk of ciguatera poising increases after events that disturb coral reefs, such as tsunamis. The risk for travellers is higher for those who sport fish and eat their catch, those who eat fish that weigh more than 3kg, and those who eat the heads, organs, intestines, and roe (egg) of reef fish.
What are the symptoms?
The symptoms of ciguatera poisoning depend on the size and species of fish and the amount and parts of the fish eaten. Initial symptoms begin within 12 hours and include gastrointestinal symptoms of diarrhea, abdominal cramps, nausea, and vomiting, which may last several days. Neurological symptoms then follow including:
- Tingling of the arms, legs, lips, mouth, and throat
- Tooth pain
- Muscle pain
- Blurred vision
- Temperature reversal (hot things feel cold and cold things feel hot)
- Feeling tired
Neurological symptoms usually resolve within weeks but can last for several months. Cardiac symptoms can also occur including irregular heartbeat, low blood pressure and shock. Most people completely recover from ciguatera poisoning, but it can be fatal in very rare cases.
Is there a treatment?
There is no cure for ciguatera poisoning and symptoms will usually resolve on their own. Treatment is supportive, including cardiac support, and replacement of fluids and electrolytes.
There is no vaccine available to prevent ciguatera poisoning. The only way to prevent ciguatera is to avoid eating large reef fish that could be contaminated by ciguatoxins including:
- Moray eel
- Sea bass
If it is not possible to completely avoid eating these fish then avoid eating reef fish that weigh more than 3kg, although smaller fish can also carry the toxins. Also avoid eating heads, organs, intestines and fish roe. Avoid eating any fish that is considered dangerous by the locals at your destination.
So now you’ve learned about ciguatera, a lesser known food-borne illness that might pose a risk on your travels. So before you order a snapper for dinner on your next Caribbean vacation, you may want to think twice!
TravelSafe Clinical Educator – Kristin Cain, RN, BSc, MSc(A)